Hack Correlation

As I wrote in the previous article , the barebones design has been through some basic testing - 500km mixed environment driving - and has been mostly successful so far. I had a suspicion that the output impedance of the circuit must somehow match a known impedance, but was not sure which. The clue was that the RaceChip unit raised city consumption by 5-15% even though it had no effect during the bench testing. Here's a datasheet for a similar Bosch pressure sensor: http://rb-aa.bosch.com/boaasocs/index.jsp;jsessionid=A20738712FCFB9E51CA919DD7D2F9E91.sundoro2?ccat_id=275&prod_id=516 For testing they are using a pull-up resistor, so on the input side of the ADC the same circuit must be simulated in order to drive the sensor. I used a 10k resistor, but perhaps even the internal pull-up could work. At the DAC/PWM output I found out that a 1.5k resistor was too large and could not sink the ECU input line low enough. With a 10ohm resistor it seemed to work fine, perhaps 47oh...

There are many variables needed to get a reliable product, so while taking a break from the ISO automotive requirements I thought of playing with a barebones design - just an Arduino, an HC-05 module and perhaps a few passives. Concept - this is similar to what the boxes on the market do - read the value on ADC, output the modified value with PWM. I'm using an Arduino Nano for this, took about half a day including the 'preview' spreadsheet. Nano pinout: Vcc to sensor supply (5V), from ECU GND to sensor ground A0 the output from the sensor Pin 9 goes to ECU (former sensor data) TX goes to RX of HC05 RX goes to TX of HC05 Notes: A0 should probably be pulled up to Vcc through a 1k resistor, I haven't tested this yet. Perhaps the Arduino weak pull-up would work. Pin 9 (PWM output) should go through a resistor and capacitor connected to ground, 1k with 0.3u looks good in my tests. The first two pictures show the Android phone connected to th...

As seen from my previous post and the sources enumerated in it there are several competing designs on the market that basically achieve the same thing - apply a negative offset to the rail sensor voltage. Since none of them offer a desirable amount of control (for the price) I'm open sourcing an own design. Goals: full programmability - curves, upper and lower threshold limits telemetry reasonably fail-safe MCU agnostic - as far as possible preserve the original waveform signal easy to make - should not require exotic or expensive components The overall architecture is simple: read sensor data into the microcontroller, process the signal, send an analog (PWM) signal out. Disclaimer: this is probably not road-legal in many countries (missing certifications) and it might break the car subject. I am not responsible if anything bad happens, do it at your own risk. However, it's not all dark, as I've already written there should be no damage as the unit still ...